Out-of-Plane Measurement of theD(e, e′p)Coincidence Cross Section

Abstract

The D(e,e'p) coincidence cross section was measured at angles out of the plane, at an excitation energy of approximately 18 MeV and a momentum transfer of 0.33 fm _1 . This is the first reported measurement of the longitudinal-transverse and transverse-transverse interference terms of the electrodisintegration cross section of the deuteron. The longitudinal plus transverse cross section is also reported. The results are in good agreement with a theoretical calculation carried out with use of the Paris potential.PACS numbers: 25.30.Fj, 25.10,+s, 27.10.+h With the advent of high-duty-cycle electron accelerators, new types of experiments, such as coincidence experiments 1,2 and polarization experiments, 3,4 have become possible. These experiments have the potential to become very powerful tools for probing nuclear structure and the nuclear force.The deuteron, as a two-nucleon system, is of great importance in the investigation of the TV-TV interaction, and thus providing a surer foundation for the study of heavier nuclei. Of special interest in the case of the deuteron is the study of interaction effects such as mesonic-exchange currents (MEC's) and the influence of nuclear isobar configurations (IC's). 5 ' 6 Relativistic effects are also of interest in the reaction. 7 Although the importance of an out-of-plane measurement inThe expression for the cross section includes two interference terms involving the longitudinal-transverse (&LT) and the transverse-transverse (OTT) cross sections in addition to the longitudinal (a L ) and transverse (a T ) components. These interference terms are not present in inclusive electron-scattering experiments, where no outgoing nucleons are detected. The interference terms are expected to give new information about the TV-TV interaction. The transverse-transverse term, in particular, is sensitive to the existence of MEC's and IC's. According to Eq. (l), an out-of-plane measurement of the coincidence cross section enables the interference terms to be separated from other components.We measured the D(e,e'p) coincidence cross section in reaction planes at 0=45°, 90°, and 135°, and at excitation energies of approximately 18 MeV. A deuterat-coincidence experiments was mentioned some time ago, 6 no experiments have actually been made, because such experiments are difficult to perform with pulsed electron accelerators. The pulse stretcher 8 constructed at Tohoku University made it possible to perform such coincidence experiments. The out-of-plane coincidence experiment for the D(e,e'p) reaction is one of the first such experiments using the high-duty electron beam.In the (e.e'p) coincidence experiment, the direction of the emitted proton momentum p is determined by two angles: 0 P , the polar angle between p and the momentum transfer q, and 0, the azimuthal angle between the scattering plane and the reaction plane. The situation is shown in Fig. 1. The coincidence cross section in the laboratory frame is given by (1) FIG. 1. Geometry of the coincidence D(e,e'p) experiment in the laborato...

Deuteron Electrodisintegration in theΔ-Resonance Region

“…The measurement of f TT is more difficult, since it requires the detection of protons outside of the electron scattering plane. Hitherto, only one measurement [6] has been reported, at very low transferred energy and momentum ͑v, jqj͒ ͑18 MeV, 160 MeV͞c͒; the f TT results were not significantly different from zero.Although the effects of D isobar currents (IC) are small in quasifree kinematics, they are expected to become important at higher excitation energies. In the Dresonance region, which corresponds to an np invariant mass W np of about 2.17 GeV, one has to treat the D isobar and the nucleon degrees of freedom in a coupledchannel (CC) approach, as was shown for NN scattering in Ref.…”

“…The measurement of f TT is more difficult, since it requires the detection of protons outside of the electron scattering plane. Hitherto, only one measurement [6] has been reported, at very low transferred energy and momentum ͑v, jqj͒ ͑18 MeV, 160 MeV͞c͒; the f TT results were not significantly different from zero.…”

“…In the unpolarized ͑e, e 0 p͒ reaction, the information on the dynamics of the two-nucleon system is contained in four structure functions: the longitudinal f L , the transverse f T , and the interference terms f LT and f TT . Measurements of the differential cross section and in some cases of the individual structure functions f L , f T , and f LT [3][4][5][6][7][8][9][10][11][12][13][14][15] have provided stringent tests of the existing theoretical models [16][17][18][19]. In particular, the f L and f T data were reproduced by the existing calculations [7,10], while the f LT data pointed to the need for a relativistic form of the current operator [8,[11][12][13][14].…”

H2(e,e′p)nReaction at High Recoil Momenta

“…Models which succeed under such stringent tests may then be applied with some confidence to infer aspects of the deuteron short-distance structure in the ''parallel kinematics'' configuration (i.e., protons detected alongq q ) where p r can be large while influences from FSI and two-body currents are expected to be minimized [7]. There is a substantial body of data for the 2 He; e 0 pn reaction, including cross-section measurements [8][9][10][11] as well as separations of various response functions [12][13][14][15][16][17][18][19][20][21] which differentiate between absorption of longitudinal and transverse photons. However, truly systematic studies of this reaction have been hindered by limitations of the various accelerators.…”

Nucleon Knockout by Intermediate Energy Electrons

“…For example, in nonrelativistic (NR) calculations is expected to be particularly sensitive to relativistic corrections of the current operator, (156) while is expected to be particularly sensitive to meson-exchange and isobar contributions (NR+MEC+IC). (154,155) The first experiment to use outof-plane detection of the ejectile was made using the pulse-stretcher ring at Sendai by Tamae et al (153) for the reaction using 129 MeV electrons scattered by…”